At the Con last night, I saw a guy wearing a black t-shirt. It had a calculus formula of some sort, an integral I think? I don't know; it's been almost 15 years since I've needed any calculus. The fellow next to me said it was clever, so I asked him what it meant. He said the math resolved to "69". The equation was followed by a question mark.

The guy wearing the shirt said, "I figure that if a girl is willing to take the time to calculate the answer, by then she probably won't slap me."

I smiled, saying thoughtfully, "You know, back when I would have been able to solve that equation, I didn't know what a 69 was."

"Well, I guess things change as you mature," said somebody else nearby.